K-解析函数的Hilbertert边值问题

定义和讨论了K-解析函数在典型域S~+={z:|z(k)|1}外的K-对称扩张函数,利用它把K-解析函数的Hilbert边值问题转化为Riemann边值问题,得到了K-解析函数类F(D(k))中Hilbert边值问题与Dirichlet边值问题的可解条件及其解的表达式.而解析函数和共轭解析函数都是K-解析函数的特例,所得结果,包含了解析函数和共轭解析函数中的相应结论.     

求“k”值的解析与感悟

反比例系数k是反比例函数y=k/x(k≠0)中的唯一常数,它决定着反比例函数的图像和性质.求k是求反比例函数解析式的关键步骤.在解有关反比例函数解析式的问题时,"k"起着     

单位圆周上广义Fourier积分的收敛性

本文研究了复平面单位圆上的广义Fourier积分.利用经典的Fourier分析的结果和Carleson定理,以及复平面上解析函数在高阶导数下直角坐标和极坐标之间的关系,我们得到了前面定义的广义Fourier积分的一个收敛定理,从而推广了直线上经典Fourier积分的收敛结果.     

周期函数Fourier级数展开式的唯一性

以2τ为周期的函数f（x）也可看作周期为2kτ（k=1,2,3…）。设f(x)满足Dirichlet充分条件,[2]证明了按[1]方法展开的以2τ为周期的Fourier级数和以4τ为周期的Fourier级数对应的不同表达形式是一致的。本则在[2]的基础上,进一步证明了按[1]方法展开的以2τ为周期的Fourier级数和以2kτ（k=1,2,3,…）为周期的Fourier级数对应的表达式的一致性,从而得出结论：任一周期函数f(x）按[1]方法展开的Fourier级数是唯一的。     

学习反比例函数五重视

反比例函数y=k/x(k为常数且k≠0)是一种基本函数,在初中阶段,主要学习它的图像、性质、函数解析式的求法及其简单的应用.下面从五个方面谈一下怎样学好反比例函数.     

一类数项级数和的表示

求出函数f(x)=xk的Fourier系数并将其代人Parseval等式,继而利用第二数学归纳法可证明:数项级数∞∑n=1 1/n2k的和能够表示为π2k/dk的形式.其中对于任意确定的k值.dk以为一常数.证明过程同时给出了求解dk的方法.     

Douglis代数意义下的超复函数空间上的T~n算子及其性质

§1 引 言 在研究一阶椭圆型方程组时,Douglis引进了Douglis代数后,把一阶椭圆型方程组化成非常简洁的形式, Dw+Aw+Bw=C (1.1)所谓超复数a定义为如下形式a=sum from k=0 to r(a_ke~k,a_k)为复数,a_0为a的复部分,sum from k=1 to r(a_ke~k)为幂零部分。而A、B、C、w为超复函数,D为微分算子,D=+q,q=sum from k=1 to r(q_k~((z)e~k)),Dw=0的正规解称为超解析函数,(1.1)的齐次方程的正规解称为广义超解析函数,对于超解析函数与广义超解析函数已有不少人进行了研究,在这些文章中引进了Pompieu算子即为J_G算     

周期函数Fourier级数展开式的唯一性

以 2 l为周期的函数 f(x)也可看作周期为 2 kl(k=1 ,2 ,3 ,… ) .设 f(x)满足 Dirichlet充分条件 ,[2 ]证明了按 [1 ]方法展开的以 2 l为周期的 Fourier级数和以 4l为周期的 Fourier级数对应的不同表达形式是一致的 .本文则在 [2 ]的基础上 ,进一步证明了按 [1 ]方法展开的以 2 l为周期的 Fourier级数和以 2 kl(k=1 ,2 ,3 ,… )为周期的 Fourier级数对应的表达式的一致性 ,从而得出结论 :任一周期函数 f(x)按 [1 ]方法展开的Fourier级数是唯一的 .     

一类解析函数的邻域

对于δ≥0及单位圆内的解析函数 f(z)=z+a_2z~2+…,定义 f(z)的δ-邻域为由满足条件 sum from k=2 to ∞ k|a_k-b_k|≤δ的解析函数 g(z)=z+b_2z~2+…所组成。本文决定了一类关于对称点凸象的函数族的δ-邻域属于一类关于对称点星象的函数族的充分条件。     

地下结构物在爆炸冲击波作用下的动力分析

提出了一种求解任意形地下结构物在爆炸冲击波作用下的动应力集中问题的半解析方法．爆炸冲击波以平面SH波的形式入射,并用Fourier变换方法将其转换到频域,不同形状地下结构物的导纳函数由复变函数和保角映射的方法求得．利用Fourier逆变换,进一步合成得到时域中的地下结构的动力响应,最后,对正方形、三角形及马蹄形孔洞附近的动应力集中系数作了数值计算,并给出了具体结果．     

On the Best Approximation in the Mean of Functions of a Complex Variable by Fourier Series in the Bergman Space

Russian Mathematics - In a simply connected domain of the complex plane, we consider the problem of mean-square approximation of analytic functions by Fourier series in orthogonal systems. For some...     

Finite convergence over a field of power series

In this paper, we define an analog of power series functions over R, when R is replaced by K = k((x))^τ , a field of generalized power series with coefficients in an ordered field k and exponents in an ordered abelian group τ. To this end for any power series S(Y)ε K[[Y]] and any y ε K, we define a notion of convergence of S(y). Thus to any power series S(Y) is associated a partial function S : K→ K. We show that these partial functions have a lot of similarities with analytic functions over R. Then we prove properties of zeros of such functions which extend properties of roots of polynomials over k((x))^τ.     

Fourier-Padé approximations and filtering for spectral simulations of an incompressible Boussinesq convection problem

In this paper, we present rational approximations based on Fourier series representation. For periodic piecewise analytic functions, the well-known Gibbs phenomenon hampers the convergence of the standard Fourier method. Here, for a given set of the Fourier coefficients from a periodic piecewise analytic function, we define Fourier-Padé-Galerkin and Fourier-Padé collocation methods by expressing the coefficients for the rational approximations using the Fourier data. We show that those methods converge exponentially in the smooth region and successfully reduce the Gibbs oscillations as the degrees of the denominators and the numerators of the Padé approximants increase.

Numerical results are demonstrated in several examples. The collocation method is applied as a postprocessing step to the standard pseudospectral simulations for the one-dimensional inviscid Burgers' equation and the two-dimensional incompressible inviscid Boussinesq convection flow.

     

Uniform and L-convergence of Logarithmic Means of Walsh-Fourier Series

The （NSrlund） logarithmic means of the Fourier series of the integrable function f is： 1/lnn-1∑k=1Sk（f）/n-k, where ln：=n-1∑k=11/k. In this paper we discuss some convergence and divergence properties of this logarithmic means of the Walsh-Fourier series of functions in the uniform, and in the L^1 Lebesgue norm. Among others, as an application of our divergence results we give a negative answer to a question of Móricz concerning the convergence of logarithmic means in norm.     

A Padé-based algorithm for overcoming the Gibbs phenomenon

Truncated Fourier series and trigonometric interpolants converge slowly for functions with jumps in value or derivatives. The standard Fourier–Padé approximation, which is known to improve on the convergence of partial summation in the case of periodic, globally analytic functions, is here extended to functions with jumps. The resulting methods (given either expansion coefficients or function values) exhibit exponential convergence globally for piecewise analytic functions when the jump location(s) are known. Implementation requires just the solution of a linear system, as in standard Padé approximation. The new methods compare favorably in experiments with existing techniques.     

Vilenkin-Like系统的不等式

For bounded Vilenkin-Like system, the inequality is also true：
（∑ k=1 ^∞ kp-2｜f^^（k）｜^p）^1/p ≤ C｜｜f｜｜Hp, 0 〈 p ≤ 2,
where f^^（·） denotes the Vilenkin-Like Fourier coefficient of f and the Hardy space Hp（Gm） is defined by means of maximal functions. As a consequence, we prove the strong convergence theorem for bounded Vilenkin-Like Fourier series, i.e.,
（∑ k=1 ^∞ k^p-2｜｜Skf｜｜p^p）^1/p≤C｜｜f｜｜Hp,0〈p〈1.     

有理Fourier级数在变差条件下的收敛性研究

本文把Fourier级数的一些经典结论推广到有理Fourier级数的情况下. 首先给出了有理Fourier级数和共轭有理Fourier级数在有界变差条件下的收敛速度估计. 利用此结论, 得到了类似于Fourier级数的Dirichlet-Jordan定理和W. H. Young定理. 最后, 证明了这两个定理在调和有界变差条件下也成立.     

On Fourier–Jacobi expansions of real analytic Eisenstein series of degree 2

We discuss the Fourier–Jacobi expansion of certain vector valued Eisenstein series of degree $2$ , which is also real analytic. We show that its coefficients of index $\pm 1$ can be described by using a generating series of real analytic Jacobi forms. We also describe all the coefficients of general indices in suitable manners. Our method can be applied to study another Fourier series of Saito-Kurokawa type that is associated with a cusp form of one variable and half-integral weight. Then, following the arguments in the holomorphic case, we find that the Fourier series indeed defines a real analytic Siegel modular form of degree 2.     

Adaptive Decomposition by Weighted Inner Functions: A Generalization of Fourier Series

In recent study adaptive decomposition of functions into basic functions of analytic instantaneous frequencies has been sought. Fourier series is a particular case of such decomposition. Adaptivity addresses certain optimal property of the decomposition. The present paper presents a fast decomposition of functions in the $\mathcal {L}^{2}(\partial {\mathbb{D}})$ spaces into a series of inner and weighted inner functions of increasing frequencies.     

Real analytic curves in Fréchet spaces and their duals

The following results are presented: 1) a characterization through the Liouville property of those Stein manifoldsU such that every germ of holomorphic functions on xU can be developed locally as a vector-valued Taylor series in the first variable with values inH(U); 2) ifT is a surjective convolution operator on the space of scalar-valued real analytic functions, one can find a solutionu of the equationT u=f which depends holomorphically on the parameterz wheneverf depends in the same manner. These results are obtained as an application of a thorough study of vector-valued real analytic maps by means of the modern functional analytic tools. In particular, we give a tensor product representation and a characterization of those Fréchet spaces or LB-spacesE for whichE-valued real analytic functions defined via composition with functionals and via suitably convergent Taylor series are the same.